Process for preparation of viscose regenerated cellulose fibers



United States Patent 3,381,075 PRGQESS FGR PREPARATION OF VISCQSE REGENERATED CELLULOSE FIBERS Ziitoshi Tonemi, Yoichi Uchida, and Tatsuo Fujii, Ewal-zuni-shi, Yamaguchi-ken, Japan, assignors to Teijin Limited, Osaka, Japan, a corporation of Japan No Drawing. Filed May 27, 1963, 521'. No. 283,540 Claims priority, application Japan, May 28, 1962, 37/21,065 2 Claims. iCl. 264-193) The present invention relates to a process for the preparation of regenerated cellulose fibers having excellent properties from viscose. More specifically, the invention relates to a method of preparation of staple fibers and filaments of high wet and dry strength as well as excellent knot strength. That is, the fibers produced in accordance with the present invention are highly resistant to stresses exerted in the direction of the fiber axis as Well as to any stress which may be exerted perpendicular to the fiber axis.

Prior to the present invention, industrially-manufactured staple fibers had very poor dry and wet strength and suffered other disadvantages which made them unacceptable on an industrial scale. In recent years, a great deal of work has been done in Japan and Europe on the development of a new type of fiber to replace the conventional staple fibers. The new type of fibers are called Polynosic-type fibers which have high dry and Wet strength. However, the Polynosic-type fibers sufier from the disadvantage that their knot strength is not satisfactory for commercial use. That is, the insufiicient knot strength causes serious difiiculties during post treatments of the fiber such as spinning or finishing of fabrics.

From the standpoint of productivity, compared with conventional staple fibers, Polynosic fibers are still very low. Therefore a great deal of research work has been conducted to overcome the drawbacks of the prior-art filaments.

It has been noted in the Japanese Ofiicial Patent Gazette, publication No. 8460/1957, that in the production of a viscose having a high degree of polymerization, a monoamine may be added and dissolved in the viscose as well as spinning the viscose in a dilute acid bath containing not more than one percent zinc sulfate. By this technique there has been some improvement in the knot strength of the produced fiber; however, fibers produced by this technique have been found unacceptable because they suffer from an insufiicient dry and Wet strength.

Another procedure disclosed in the Japanese Ofiicial Patent Gazette, publication No. 3106/1960, was one which suggested adding a monoamine during the reaction in the production of a viscose of a high degree of polymerization and spinning the same in a dilute acid bath containing only sulfuric acid. This procedure was instituted in an attempt to raise the knot strength of the product. However, by virtue of the cost of the monoamine, the process suffered industrial rejection because of the cost of the product. In addition, because of the procedural steps, the spinning system was complicated and equipment cost became economically unfeasible.

However, it has been found in accordance with the process of the present invention, that regenerated cellulose fibers from viscose may be produced which have superior dry and wet strengths to those of cotton and which at the "ice same time have industrially acceptable knot strength and which process is acceptable from the standpoint of economy.

The process of this invention comprises producing alkali cellulose of a relatively high degree of polymerization and of uniform structure, that is, distribution of degree of polymerization is uniform, and of the three steps for preparing viscose from such alkali cellulose: to wit, the first step of adding (MS-0.3% of an alkylene oxide polymer, or an adduct of amine and alkylene oxide, or an acid amide, to the solution of the xanthate prepared from the alkali cellulose as described; the second step o coagulating the viscose in a spinning bath containing 0.005-0.3% of a divalent metallic salt; and the third step of regenerating the as-spun filaments having a suitable degree of regeneration through the second bath.

With respect to the pulp useful in the present invention, it is preferred that pulp be utilized having an average degree of polymerization of 1200 or more. By steeping the pulp in alkali, shredding, and aging the same at below 20 C. for not less than 10 hours, alkali cellulose of high degree of ploymerization and of very even distribution of polymerization can be obtained.

When said alkali cellulose is xanthated with, say, more than 40%, preferably 40-70%, of carbon disulfide, because of the even distribution of degree of ploymerization of the alkali cellulose, very well xanthated viscose which is easily soluble in alkali of lower concentration than is required for conventional xanthate or in pure water and furthermore which has good dispersion property is obtained.

In conventional processes for preparation of highly polymerized viscose the viscosity of the viscose is generally too high, industrially its filtration is difficult, deaeration is insufficient, and spinning operation may be hindered. However, in accordance with the process of the present invention, i.e., because the dispersion state of the xanthate is very good, viscose of satisfactory viscosity for industrial use in spite of its high degree of polymerization can be obtained, and such troubles inherent in the conventional processes can be avoided.

The gist of this invention lies, in addition to such process for production of viscose, in the concept of adding such substances as polyalkyleue oxide, acid amide, adduct of amine and alkylene oxide, etc. to the dissolving solution at the viscose-dissolving step, making viscose and Spinning the same.

Because these substances generally possess surface active properties, they serve to better the dispersion state of xanthate in the alkali solution. Furthermore because they greatly influence, together with byproducts in the viscose, permeation and diffusion of hydrogen ion and divalent metallic ion to the filaments at the time of spinning of the viscose, it is possible to optionally adjust the state of coagulation and regeneration of the viscose flow by varying the amount of addition of these substances.

The process of the present invention makes such controls possible for an industrial process for the first time. Moreover, optimum results with said viscose can be obtained by spinning the same in a spinning bath containing at least 0.005% but not more than 0.3% of a divalent metallic salt.

When the amount of the metallic salt is ess than 0.005%, the aforesaid advantages of the viscose-additives are hardly recognizable, whereas if it is more than 0.3%,

spun state becomes very unstable, and the objects of this invention cannot be accomplished.

However, the amount of addition must of course be fitted to the temperature of the spinning bath. At such a low concentration as close to 0.005%, a relatively low temperature should be employed, whereas at a high concentration of about 0.3%, a high temperature of above 40 C. is required. This is why the temperature of the spinning bath should be within the specified range of 20-45 C.

Still another critical feature of the present invention is the use of a second bath in addition to the first bath described above. That is, even under the optimum conditions for production of the viscose and of the spinning bath, without the use of a second bath, the achievements as of this invention cannot be expected.

Because the as-spun filaments emerged from the spinning bath are not yet completely regenerated, a suitable method for an ideal regeneration is also very important.

In the conventional two-bath system, the second bath has been provided only for the purpose of aiding the regeneration of filaments, and no particular care has been taken for the formation process of the filaments in the second bath.

It has been discovered that the regeneration conditions in the second bath have an important bearing on the nature of the product, and we therefore carefully examined the concentration and temperature conditions of the second math to establish specific conditions fitted to manifest the inherent capacity of the filaments to the maximum.

A general practice in accordance with the present process shall be described hereinbelow.

That is, as aforesaid, pulp of an average degree of polymerization of, preferably 1200 or more is steeped in alkali, shredded, and aged for at least 10 hours at below 20 C., to yield an alkali cellulose of high average degree of polymerization and further of even distribution of polymerization.

Said alkali cellulose is xanthated with, for example, 40% or more of carbon disulfide, and the resultant good xanthate is dissolved in diluted caustic soda solution or pure water containing additives listed below, to make a viscose containing 48% of cellulose, 3-6% of alkali, and 0.15-0.3% of the additives. The additives useful in the present invention are as follows: polyalkylene om'de, acid amide, and adduct of amine and alkylene oxide.

As the polyalkylene oxide, those of general formula wherein:

R and R are selected from the group consisting of hydrogen, alkyl or aryl groups having more than 4 but not more than 10 carbon atoms, and may be same or different,

n is a positive integer of 2-10 and m is a positive integer of 5-100 are used.

As said alkylene oxide polymer, it may be a polymethylene oxide polymer having the formula:

2)n lm wherein R, R, n, m have the same signification as above or an alkylene oxide polymer having side chains, e.g.,

a propylene oxide of the formula RO C|1H-CH2-O)R' CH wherein R and m have the same signification as above.

The acid amide may be represented by the formula 'RCONH wherein R is an alkyl or alkyl group of 1-18 carbon atoms.

As the amine-alkylene oxide adduct, those having the following formula may be used:

(CnH no),R' 2 RN\ (onHm0),R"

wherein:

R and R are selected from the group consisting of hydrogen, alkyl, or aryl groups having more than 4 but not more than 10 carbon atoms, and may be same or different,

n is a positive integer of 2-10, and

x+y is a positive integer of 5-100, preferably 5-20.

Next the composition of the coagulation bath must be such that the bath contains not more than 5% of sulfuric acid, not more than 15% of sodium sulfate, and 0.005-0.3% of a divalent metallic salt, such as divalent sulfate of Zn, Ni, Co, Cd, and Cr. The temperature of the spinning bath should be maintained not higher than 45 C.

Then the filaments of which regeneration value before entering into the second bath is adjusted to 4060% are passed through the second bath of a temperature above C. containing not more than 1.5% of sulfuric acid and wound up with tension.

As aforesaid, by the practice of the present process the dispersion state of the viscose becomes very good, and consequently the filament formation at the time of spinning is accomplished very evenly. Thus, while in the past viscose of high degree of polymerization was spinnable only at a very low rate of spinning, in this invention the spinning rate is markedly increased without adversely affecting the quality of the product filaments. Spinning stability also is unchanged from that in case of low speed spinning.

' Example 1 Wood pulp having a degree of polymerization of 1200 was steeped in an 18.5% caustic soda solution for 2 hours at 20 C., pressed 2.60 times, shreaded for 2 hours at 15 C. and thereafter aged for 13 hours at 15 C. to obtain an alkali cellulose having a degree of polymerization of about 800. Next 47% of carbon disulfide, based on the cellulose content of the alkali cellulose, was added, and the alkali cellulose was xanthated for 3 hours at 25 C., after which it was dissolved for 3 hours at 10 C. in a dilute alkaline solution containing 15-dendrophenol (a compound of the following formula:

i.e., a monophenol ether of polyalkylene glycol) to obtain a viscose having a cellulose concentration of 5.0%, an alkali concentration of 2.9%, a viscosity of 380 poises and a 'y-value of 78.

After filtering and deaerating the viscose, it was immediately extruded through a spinneret having 5000 orifices of a diameter of 0.06 mm. into a spinning bath of a temperature of 20 C. and containing 0.03% zinc sulfate, 3% sulfuric acid and 5.0% sodium sulfate wherein the resultant filaments were wound up on a first step godet with a draft of 0.75 and then conducted to a second bath having a sulfuric acid concentration of 1.0% and a temperature of C., when the regeneration value was 55% followed by winding up, cutting and refining. The spinning speed at this time was 30 meters per minute.

The properties of the fiber so obtained was as shown as A in Table I. In the table, B is that whose other processing steps were completely identical to that of the process of this invention, but in which the viscose preparation process the material pulp used was that having a degree of polymerization of about 800, aging was not performed and the degree of polymerization of the product was made to be about the same as that according to the present invention. C in the table is that in which the viscose preparation process was completely identical to the process of this invention, but in which an additive was not incorporated during dissolving. D, on the other hand, is that in which the viscose preparation step was identical to that of this invention, but in which the spinning bath did not contain a divalent metallic salt.

TABLE I Dry Wet Dry Wet Knot Denier Strength, Strength, Elongation, Elongation, Strength,

g./de. g./de. Percent Percent g/de.

Denier 1.25 Dry strength g./de 4.01 Wet strength g./de 2.98 Dry elongation "percent" 12.6 Wet elongation do 14.8 Knot strength g./de 2.22

What we claim is:

1. In a process for the preparation of regenerated cellulose fibers from viscose, the improvement which comprises producing cellulose xanthate from an alkali cellulose having a relatively high degree and even distribution of polymerization which has been obtained by using pulp having an average degree of polymerization of not less than 1200, adding and dissolving in the cellulose xanthate an additive selected from the group consisting of an alkylene oxide polymer, an adduct of an amine with an alkylene oxide, and an acid amide to make a viscose, said additive being added in such proportion that the viscose contains 0.15 to 0.30 percent of the same, spinning said viscose at a temperature of C. to 45 C. in a first spinning bath containing 0.0050.3 percent of a divalent metallic salt, thereafter subjecting the resultant filaments having a regeneration value of -60 percent to tension in a second bath having a temperature of at least C. and a sulfuric acid concentration of not more than 1.5 percent.

2. A process in accordance with claim 1 wherein the alkali cellulose is obtained by a process which consists of steeping pulp having an average degree of polymerization of not less than 1200 in alkali, shredding the resultant alkali cellulose, and thereafter aging the same for ten to 20 hours at a temperature not higher than about 20 C.

References Cited UNITED STATES PATENTS 3,109,700 11/1963 Klein et al. 106165 2,974,004 3/1961 Heuer et a1. 264-197 2,997,365 8/1961 Smith et a1. 264-197 3,108,849 10/1963 Owashi et a1.

3,109,698 11/1963 Klein et a1. 264-197 3,126,435 3/ 1964 Tallis et al.

3,139,467 6/1964 Drisch et al.

3,226,461 12/1965 Wise et a1. 264--197 3,082,057 3/ 1963 Walker 1854 3,232,779 2/ 1966 Schoenfeld et a1. 106165 JAMES A. SEIDLECK, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

A. KOECKERT, B. SNYDER, Assistant Examiner. 

1. IN A PROCESS FOR THE PREPARATION OF REGENERATED CELLULOSE FIBERS FROM VISCOSE, THE IMPROVEMENT WHICH COMPRISES PRODUCING CELLULOSE XANTHATE FROM AN ALKALI CELLULOSE HAVING A RELATIVELY HIGH DEGREE AND EVEN DISTRIBUTION OF POLYMERIZATION WHICH HAS BEEN OBTAINED BY USING PULP HAVING AN AVERAGE DEGREE OF POLYMERIZATION OF NOT LESS THAN 1200, ADDING AND DISSOLVING IN THE CELLULOSE XANTHATE AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF AN ALKYLENE OXIDE POLYMER, AN ADDUCT OF AN AMINE WITH AN ALKYLENE OXIDE, AND AN ACID AMIDE TO MAKE A VISCOSE, SAID ADDITIVE BEING ADDED IN SUCH PROPORTION THAT THE VISCOSE CONTAINS 0.15 TO 0.30 PERCENT OF THE SAME, SPINNING SAID VISCOSE AT A TEMPERATURE OF 20*C. TO 45*C. IN A FIRST SPINNING BATH CONTAINING 0.005-0.3 PERCENT OF A DIVALENT METALLIC SALT, THEREAFTER SUBJECTING THE RESULTANT FILAMENTS HAVING A REGENERATION VALUE OF 40-60 PERCENT TO TENSION IN A SECOND BATH HAVING A TEMPERATURE OF AT LEAST 80*C. AND A SULFURIC ACID CONCENTRATION OF NOT MORE THAN 1.5 PERCENT. 